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<b><i>env</i> <b>txn</b></b>
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<b><pre>env txn
	[-nosync]
	[-nowait]
	[-parent txnid]
	[-sync]
</pre></b>
<b>Description(env txn)</b>
<p>The <i>env</i> <b>txn</b> command begins a transaction.  The returned transaction
handle is bound to a Tcl command of the form <b>env.txnX</b>, where
X is an integer starting at 0 (for example, env0.txn0 and env0.txn1).
It is through this Tcl command that the script accesses the transaction
methods.</p>
<p>The options are as follows:</p>
<br>
<b>-nosync</b><ul compact><li>Do not synchronously flush the log when this transaction commits or
prepares. This means the transaction will exhibit the ACI (atomicity,
consistency, and isolation) properties, but not D (durability); that
is, database integrity will be maintained, but it is possible that this
transaction may be undone during recovery instead of being redone.
<p>This behavior may be set for an entire Berkeley DB environment as part of the
<b>berkdb env</b> call.</p></ul>
<b>-nowait</b><ul compact><li>If a lock is unavailable for any Berkeley DB operation performed in the context
of this transaction, throw a Tcl error immediately instead of blocking on
the lock.</ul>
<b>-parent txnid</b><ul compact><li>Create the new transaction as a nested transaction, with the specified
transaction indicated as its parent.  Transactions may be nested to any
level.</ul>
<b>-sync</b><ul compact><li>Synchronously flush the log when this transaction commits or prepares.
This means the transaction will exhibit all of the ACID (atomicity,
consistency, isolation, and durability) properties.
<p>This behavior is the default for Berkeley DB environments unless the
<b>-nosync</b> option was specified to the <b>berkdb env</b> call.</p></ul>
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<p>The <i>env</i> <b>txn</b> command returns a transaction handle on success.</p>
<p>In the case of error, a Tcl error is thrown.</p>
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